Systems and methods for controlling use of power in a computer system

ABSTRACT

In one embodiment, a power adapter comprises a power supply to output power for powering a powered device. The power adapter outputs information indicative of an amount of power output by the power supply for use by the powered device to control the amount of power used by the powered device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationhaving Ser. No. 11/250,596 filed Oct. 14, 2005 now U.S. Pat. No.7,526,659. This application claims the benefit of U.S. ProvisionalPatent Application Ser. No. 60/649,448, filed Feb. 1, 2005, which isincorporated by reference herein.

BACKGROUND

One way in which power is supplied to a portable computer is by using apower adapter. The power adapter is coupled to an alternating current(AC) power source (such as an AC outlet) and converts an AC line voltageto a lower, direct current (DC) voltage suitable for use by the portablecomputer. The power adapter is typically a unit that is separate fromthe portable computer. A portable computer is designed to be moved. Whena portable computer is moved to a new location, a power adapter is oftenbrought to the new location along with the portable computer. As result,it is desirable to reduce the size and weight of the power adapter inorder to facilitate the movement of the power adapter.

Typically, a portable-computer power adapter is designed to output aparticular nominal output voltage for load currents up to a particularmaximum current level. When the load current reaches or exceeds themaximum current level, the power adapter reduces the output voltage inorder to attempt to prevent the load current from exceeding the maximumcurrent level. Reducing the output voltage in this manner is referred toas “current limiting” the power adapter.

Typically, the power adapter powers various components of the portablecomputer (including, for example, a central processing unit (CPU),display, and a storage device such as an internal hard drive). In somesituations, the power adapter also provides power to charge a batteryhoused within the portable computer. Moreover, in some situations, thepower adapter provides power to one or more peripherals or other devicescoupled to the portable computer (for example, a docking station or anexternal drive unit such as a CD, DVD, or floppy drive unit).Consequently, a portable-computer power adapter is typically used toprovide power to a variety of loads.

One way in which a portable-computer power adapter is designed to workwith a variety of loads is to design the power adapter for the largestload that the power adapter is expected to power. Designing a powersupply in this way, however, typically results in a power adapter thatis larger, heavier, and/or more expensive than a power adapter designedto provide less power.

One way in which the size, weight, and/or cost of the power adapter canbe reduced is by reducing the largest load that the power adapter isexpected to power. As a result, a power adapter that outputs less powercan be used to power the reduced largest-expected load. One way in whichthe largest-possible load can be reduced is by reducing the amount ofpower consumed by the portable computer (for example, by reducing theclock frequency at which the portable computer's CPU is operated and/orby reducing the amount of power used to charge a battery housed withinthe portable computer). This reduction typically results in adegradation in the portable computer's performance (for example, byreducing the speed at which a CPU executes program instructions and/orincreasing the amount of time required to charge a battery).

DRAWINGS

FIG. 1 is a high-level block diagram of one exemplary embodiment of acomputing system in accordance with the invention.

FIG. 2 is a diagram showing the relationship of FIGS. 2A and 2B.

FIGS. 2A and 2B are a block diagram of one exemplary embodiment of acomputing system in accordance with the invention.

FIG. 3 is a diagram showing the relationship of FIGS. 3A and 3B.

FIGS. 3A and 3B are a block diagram of one exemplary embodiment of acomputing system in accordance with the invention.

FIG. 4 is a diagram showing the relationship of FIGS. 4A and 4B.

FIGS. 4A and 4B are a block diagram of one exemplary embodiment of acomputing system in accordance with the invention.

FIG. 5 is a high-level block diagram of one exemplary embodiment of acomputing system in accordance with the invention.

FIG. 6 is a chart illustrating exemplary values of Radp and Rnotebookfor various power ratings in one implementation of the system of FIG. 5.

FIG. 7 is a chart illustrating the voltage difference between the twoinputs of a comparator of a portable computer implemented using thechart of FIG. 6 when a power adapter implemented using the chart of FIG.6 is directly coupled to the portable computer.

FIG. 8 is a block diagram of one exemplary embodiment of a computingsystem in accordance with the invention.

FIG. 9 is a chart illustrating the voltage difference between the twoinputs of a comparator of a portable computer implemented using thechart of FIG. 6 when a power adapter implemented using the chart of FIG.6 is coupled to the portable computer via the docking station of FIG. 8.

FIG. 10 is a block diagram of one exemplary embodiment of a computingsystem in accordance with the invention.

FIG. 11 is a block diagram of one exemplary embodiment of a computingsystem in accordance with the invention.

FIG. 12 is a block diagram of one exemplary embodiment of a computingsystem in accordance with the invention.

FIG. 13 is a block diagram of one exemplary embodiment of a computingsystem.

FIG. 14 is diagram showing the relationship of FIGS. 14A and 14B.

FIGS. 14A and 14B are a block diagram of one exemplary embodiment of acomputing system in accordance with the invention.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 is a high-level block diagram of one embodiment of a computingsystem 100. The computing system 100 comprises a power adapter 102 thatis used to power at least one powered device 104. In the particularembodiment shown in FIG. 1, the powered device 104 comprises a portablecomputer 106. The portable computer 106, in the embodiment shown in FIG.1, can be powered by the power adapter 102 (when coupled thereto) or bya battery coupled to the portable computer 106 via a battery interface108. In other embodiments, one or more other external devices that arecommunicatively coupled to the portable computer 106 (for example, adocking station or an external drive unit such as a CD, DVD, or floppydrive unit) are also powered by the power adapter 102. In some otherembodiments, a power adapter is used to power other types of electronicdevices such as other types of battery-powered devices.

The power adapter 102 comprises a power-source interface 110 that isused to couple the power adapter 102 to an AC power source 112 (such asan AC outlet). The power adapter 102 also comprises a device interface114 that is used to couple the power adapter 102 to the powered device104 (the portable computer 106 in the embodiment shown in FIG. 1). Inone implementation of the embodiment shown in FIG. 1, the power adapter102 is directly coupled to the power source 112 and to the portablecomputer 106 using appropriate cabling and connectors. In anotherembodiment, the power adapter 102 is coupled to the portable computer106 indirectly via one or more intermediary devices such as a dockingstation.

The power adapter 102 also comprises a power supply 116 that converts anAC line voltage from the AC power source 112 to a lower DC voltagesuitable for use by the portable computer 106. In the embodiment shownin FIG. 1, the power supply 116 is designed to output a particularnominal output voltage on the device interface 114 for use by theportable computer 106. The power supply 116 comprises any suitable powersupply topology now known or later developed. In the embodiment shown inFIG. 1, the power supply 116 comprises a controller 118 that controlsthe voltage output by the power supply 116.

The power adapter 102 comprises a voltage sense circuit 120 thatprovides output voltage feedback to the controller 118, which uses theoutput voltage feedback to control the power supply 116. For example, inone embodiment, the output voltage feedback indicates when the outputvoltage of the power adapter 102 exceeds a nominal output voltage forthe power adapter 102. In the particular embodiment shown in FIG. 1, thevoltage sense circuit 120 comprises a voltage sense operationalamplifier 122. The voltage sense operational amplifier 122 (alsoreferred to here as the “voltage sense op amp” 122) receives a referencevoltage (referred to here as the “voltage sense reference voltage”) onthe non-inverting input of the voltage sense op amp 122. The voltagesense reference voltage corresponds to (or is otherwise indicative of)the nominal output voltage of the power adapter 102. In the particularembodiment shown in FIG. 1, the voltage sense circuit 120 comprises aZener diode 124 across which the voltage regulation op amp referencevoltage is developed using an appropriate bias resistor 126.

A voltage indicative of the output voltage VOUT of the power adapter 102is coupled to the inverting input of the voltage sense op amp 122. Thisvoltage is taken between a pair of bias resistors 128 and 130. Aresistor 132 and a capacitor 134 are coupled in series between theinverting input and the output of the voltage sense op amp 122 toprovide control stability. The output of the voltage sense op amp 122 iscoupled to an optocoupler diode 136 through a resistor 138 and a diode140.

When the output voltage VOUT of the power adapter 102 is less than orequal to the nominal output voltage of the power adapter 102, thevoltage sense op amp 122 outputs a “high voltage” value that isinsufficient to turn on the diode 140. When the output voltage VOUT ofthe power adapter 102 is greater than the nominal output voltage of thepower adapter 102, the output of the voltage sense op amp 122 falls.When the output of the op amp 122 falls enough to turn on the diode 140,current is driven through the optocoupler 136, which causes thecontroller 118 of the power supply 116 to limit the output voltage ofthe power adapter 102. The amount by which the controller 118 limits theoutput voltage of the power adapter 102 is based on the amount ofcurrent flowing through the optocoupler 136. The voltage sense circuit120 and the controller 118 implement closed-loop control of the outputvoltage of the power adapter 102.

The power adapter 102 also comprises a current sense circuit 142. Thecurrent sense circuit 142 provides load current feedback to thecontroller 118, which uses the load current feedback to control thepower supply 116. For example, in one embodiment, the load currentfeedback indicates when the load current has reached a maximum currentlevel for the power adapter 102, which causes the controller 118 toreduce the output voltage of the power adapter 102 (which in turnreduces the load current output by the power adapter 102).

In the particular embodiment shown in FIG. 1, the current sense circuit142 comprises a current sense resistor 144 through which the loadcurrent of the power adapter 102 flows. The current sense circuit 142also comprises a current sense operational amplifier 146 (also referredto here as the “current sense op amp” 146). A voltage reference(referred to here as the “current sense op amp reference voltage”) iscoupled to the non-inverting input of the current sense op amp 146. Thecurrent sense op amp reference voltage corresponds to a predeterminedthreshold load current value (also referred to here as the “throttlecurrent threshold”) for the power adapter 102. In the particularembodiment shown in FIG. 1, the current sense circuit 142 comprises apair of resistors 148 and 150 in series with the cathode of the Zenerdiode 124 and one end of the current sense resistor 144. A voltageindicative of the load current of the power adapter 102 is coupled tothe inverting input of the current sense op amp 146 by coupling theinverting input of the current sense op amp 146 to the other end of thecurrent sense resistor 144 via a resistor 152. A capacitor 154 iscoupled between the inverting input and the output of the current senseop amp 146 to provide control stability. The output of the current senseop amp 146 is coupled to the optocoupler diode 136 through a resistor156 and a diode 158.

When the load current output by the power adapter 102 is less than orequal to the throttle current threshold of the power adapter 102, thecurrent sense op amp 146 outputs a “high voltage” value that isinsufficient to turn on the diode 158. When the load current of thepower adapter 102 is greater than the throttle current threshold of thepower adapter 102, the output of the current sense op amp 146 falls. Inthe embodiment shown in FIG. 1, the current sense circuit 142 isconfigured so that when the load current reaches the maximum currentlevel for the power adapter 102, the output of the current sense op amp146 falls enough to turn on the diode 158 and drive current through theoptocoupler 136. When current is driven through the optocoupler 136, thecontroller 118 of the power supply 116 limits the output voltage of thepower adapter 102 based on the amount of current flowing through theoptocoupler 136. By reducing the output voltage of the power adapter102, the load current of the power adapter 102 is reduced or limited.The current sense circuit 142 and the controller 118 implementclosed-loop control of the load current of the power adapter 102 in anattempt to keep the load current of the power adapter 102 below themaximum current level for the power adapter 102.

The device interface 114 of the power adapter 102 comprises a pair ofpower terminals 160 that are used to provide power to the portablecomputer 106. In the particular embodiment shown in FIG. 1, the powerterminals 160 include an output voltage terminal (VOUT) and a groundterminal (GND). The device interface 114 further comprises a controlterminal 162 over which information indicative of the amount of poweroutput by the power adapter 102 is supplied to the portable computer106, which uses the information to control how much power is used by theportable computer 106. In the embodiment shown in FIG. 1, theinformation indicative of the amount of power output by the poweradapter 102 comprises a control signal output by the power adapter 102.The control signal is indicative of the amount of power output by thepower adapter 102. The power adapter 102 comprises a control signalcircuit 164 that outputs the control signal. In other embodiments, theinformation indicative of the amount of power output by the poweradapter 102 is communicated to a powered device 104 in other ways.

In the embodiment shown in FIG. 1, the control signal is a function ofthe load current output by the power adapter 102. When the load currentoutput by the power adapter 102 is less than the throttle currentthreshold, the control signal circuit 164 does not output by a controlsignal. When the load current output by the power adapter 102 exceedsthe throttle current threshold, the control signal circuit 164 outputs acontrol signal. Moreover, in the embodiment shown in FIG. 1, the amountof current output by the control circuit 164 on the control signal isindicative of how much the load current of the power adapter 102 exceedsthe throttle current threshold. The control signal circuit 164, in suchan embodiment, uses the load current feedback provided by the currentsense circuit 142 to determine when and by how much the load current ofthe power adapter exceeds the throttle current threshold. The controlsignal generated by the control signal circuit 164 is used by at leastone powered device 104 that is communicatively coupled to the controlterminal 162 to control the amount of power used by that device 104.

In the particular embodiment shown in FIG. 1, the control signal circuit164 comprises a transistor 166. The output of the current sense op amp146 of the current sense circuit 142 is coupled to the output voltageterminal VOUT of the device interface 114 via resistors 168 and 170. Thevoltage at the node between the resistors 168 and 170 is coupled to thebase of the transistor 166. The emitter of the transistor 166 is coupledto the output voltage terminal VOUT of the device interface 114 viaresistor 173. The control terminal 162 of the device interface 114 iscoupled to the collector of the transistor 166 via a diode 172. When theload current output by the power adapter 102 is less than or equal tothe throttle current threshold of the power adapter 102, the currentsense op amp 146 outputs a “high voltage” value such that the voltagedifference between the output of the current sense op amp 146 and theoutput voltage VOUT of the power adapter 102 (and the resulting currentflowing to the base of the transistor 166) is insufficient to turn onthe transistor 166.

As noted above, when the load current of the power adapter 102 isgreater than the throttle current threshold of the power adapter 102,the output of the current sense op amp 146 falls. When the output of theop amp 146 falls enough so that the voltage difference between theoutput of the op amp 146 and the output voltage of the power adapter 102is sufficient to turn on the transistor 166, a current flows from theemitter to the collector of the transistor 166. The current that flowsfrom the emitter to the collector of the transistor 166 is output on thecontrol terminal 162 as the control signal. In such an embodiment, thecontrol signal circuit 164 is configured so that when the transistor 166turns on, the current flowing from the emitter to the collector of thetransistor 166 (that is, the control signal) is proportional to thevoltage output by the current sense op amp 146, which is proportional tothe amount by which the load current output by the power adapter 102exceeds the threshold current level.

The control signal circuit 164 and/or the current sense circuit 142 areconfigured so that the control signal circuit 164 outputs the controlsignal before the power adapter 102 is current limited (if at all). Byoutputting the control signal before the power adapter 102 is currentlimited, the portable computer 106 is able to attempt to reduce theamount of power used by the portable computer 106. Where the amount ofpower used by the portable computer 106 is reduced sufficiently to keepthe load current output by the power adapter 102 below the maximumcurrent level for the power adapter 102, the power adapter 102 does notcurrent limit. For example, in the embodiment shown in FIG. 1, theresistors 156, 168 and 170 are selected so that, as the load currentoutput by the power adapter 102 rises, transistor 166 turns on anddrives the control signal on the control terminal 162 before the diode158 turns on and drives current through the optocoupler 136.

At least one of the powered devices 104 powered by the power adapter 102comprises an adapter interface that is used to couple the powered device104 to the power adapter 102. In the embodiment shown in FIG. 1, theportable computer 106 comprises an adapter interface 174. The adapterinterface 174 comprises a pair of power terminals 176 that are used toreceive power from the power adapter 102 via the power terminals 160 ofthe power adapter's device interface 114. In the particular embodimentshown in FIG. 1, the power terminals 176 include an input voltageterminal (VADP) and a ground terminal (GND) that are coupled to theoutput voltage terminal VOUT and the ground terminal GND, respectively,of the power adapter's device interface 114.

The adapter interface 174 further comprises a control terminal 178 overwhich the control signal output by the power adapter 102 is received bythe portable computer 106. The portable computer 106 uses the controlsignal to implement closed-loop feedback in order to control the amountof power used by the portable computer 106. In the particular embodimentshown in FIG. 1, a throttle signal circuit 180 uses the control signaloutput by the power adapter 102 as an input. The throttle signal circuit180 outputs a throttle signal 181 when the control signal indicates thatthe amount of power used by the portable computer 106 should be reduced.The throttle signal 181, in such an embodiment, is an input to anembedded controller 182, which causes the portable computer 106 toreduce the amount of power used by the portable computer 106 wheninstructed to do so by the throttle signal 181.

In the particular embodiment shown in FIG. 1, the throttle signalcircuit 180 uses pulse width modulation to output the throttle signal181, where the duty cycle of the throttle signal 181 is indicative ofthe amount by which the load current output by the power adapter 102exceeds the throttle current threshold. The throttle signal circuit 180,in the embodiment shown in FIG. 1, comprises a resistor 184 throughwhich the control signal is terminated to ground. The voltage developedacross the resistor 184 is coupled to the non-inverting input of acomparator 186. The inverting input of the comparator 186 is coupled toa source 188 of a sawtooth wave. The comparator 186 compares thesawtooth wave to the voltage developed across the resistor 184. Theoutput of the comparator 186 is converted to an active-low, logicvoltage level by a metal oxide semiconductor field effect transistor(MOSFET) 187 and the throttle signal 181 is taken at the drain of theMOSFET transistor 187. The output of the comparator 186 is coupled tothe gate of the MOSFET 187. The source of the MOSFET 187 is coupled toground GND and the drain of the MOSFET 187 is coupled to a logic voltagelevel (VDD) via a resistor 189.

When the load current output by the power adapter 102 is below thethreshold current level, the current flowing on the control signal iszero and the voltage at the non-inverting input of the comparator 186 iszero. As a result, for the entire period of the sawtooth wave, thevoltage on the non-inverting input of the comparator 186 will be lessthan the voltage on the inverting input of the comparator 186 and theoutput of the comparator 186 will be zero. Consequently, the transistor187 is not turned on and the throttle signal 181 has a logical highvalue (that is, is not asserted) for the entire period of the sawtoothwave (that is, the duty cycle for the throttle signal 181 is zeropercent).

The output of the comparator 186 has a non-zero value for that part ofthe period of the sawtooth wave where the voltage on the non-invertinginput of the comparator 186 is greater than the voltage on the invertinginput of the comparator 186. When the output of the comparator 186 has avalue that is sufficient to turn on the transistor 187, the throttlesignal 181 has a logical low value (that is, is asserted). In this way,the control signal is used to pulse width modulate the throttle signal181. In one embodiment, the throttle signal circuit 180 is configured sothat the duty cycle of the throttle signal 181 is zero percent when theload current output by the power adapter 102 is less than the throttlecurrent threshold. In such an embodiment, the throttle signal circuit180 is also configured so that the duty cycle of the throttle signal 181is between zero percent and one-hundred percent when the load currentoutput by the power adapter 102 is greater than the throttle currentthreshold but less than the maximum current level. In such anembodiment, the throttle signal circuit 180 is also configured so thatthe duty cycle of the throttle signal 181 is one-hundred percent whenthe load current is greater than or equal to maximum current level.

In the embodiment shown in FIG. 1, the portable computer 106 comprisesvarious computer components 190 that are used to implement variouscomputational and input/output functionality supported by the portablecomputer 106. The portable computer 106 comprises at least one centralprocessing unit (CPU) 192 and memory 194. The CPU 192 executes variousitems of software, including, for example, an operating system and oneor more applications. Typically, a portion of the software executed bythe CPU 192 and one or more data structures used by the software duringexecution are stored in the memory 194. Memory 194 comprises anysuitable memory such as, for example, random access memory (RAM), readonly memory (ROM), and/or registers within the CPU 192. In theembodiment shown in FIG. 1, one way in which the portable computer 106reduces the amount of power used by the portable computer 106 is toreduce the clock frequency at which the CPU 192 operates. In theembodiment shown in FIG. 1, the CPU 192 includes the ability to changethe clock frequency at which the CPU 192 operates in order to manage theamount of power used to operate the CPU 192.

In the embodiment shown in FIG. 1, the embedded controller 182 controlsthe operation of one or more of the other components in the portablecomputer 106. Among other things, the embedded controller 182 controlsthe amount of power used by the portable computer 106 based on thecontrol signal received on the adapter interface 174 from the poweradapter 102. The embedded controller 182, in one such embodiment,comprises a programmable processor that executes program instructions(for example, software or firmware) that cause the embedded controller182 to carry out at least a portion of the functionality described hereas being performed by the embedded controller 182. In the embodimentshown in FIG. 1, the embedded controller 182 reduces the clock frequencyat which the CPU 192 operates in order to reduce the amount of powerused by the portable computer 106. In some other embodiments, theembedded controller 182 reduces the amount of power used by the portablecomputer 106 in other ways (for example, by reducing the amount of powerused to charge a battery or by dimming a display device included in theportable computer 106) in addition to or instead of reducing the clockfrequency at which the CPU 192 operates. Moreover, in some otherembodiments, the amount of power used by the portable computer 106 iscontrolled in other ways in addition to or instead of by using anembedded controller 182.

The various components of the portable computer 106 are coupled to oneanother as needed using appropriate interfaces (for examples, usingbuses, ports, and the like).

In the embodiment shown in FIG. 1, when the load current output by thepower adapter 102 exceeds the throttle current threshold for the poweradapter 102, the control signal circuit 164 of the power adapter 102outputs the control signal. The amount of current flowing in the controlsignal is used to indicate by how much the load current output by thepower adapter 102 exceeds the throttle current threshold for the poweradapter 102. The throttle signal circuit 180 of the portable computer106 receives the control signal from the power adapter 102 on thecontrol terminal 178 and outputs the throttle signal 181 based on thereceived control signal. In the embodiment shown in FIG. 1, the throttlesignal 181 is a pulse width modulated signal where the duty cycle of thethrottle signal 181 indicates by how much the load current of the poweradapter 102 exceeds the throttle current threshold for the power adapter102. The embedded controller 182 reduces the amount of power used by theportable computer 106 by reducing the clock frequency at which the CPU192 operates based on the throttle signal 181. In the embodiment shownin FIG. 1, the embedded controller 182 uses the throttle signal 181output by the throttle signal circuit 180 to drive a stop clock input ofthe CPU 192 in order to reduce the clock frequency at which the CPU 192operates. The clock frequency of the CPU 192 is “throttled” when thethrottle signal 181 is asserted. As a result, the clock frequency of theCPU 192 is reduced by an amount that is proportional to the duty cycleof the throttle signal 181. In this way, closed-loop feedback is used tocontrol the amount of power consumed by the portable computer 106. Inother embodiments, the clock frequency of the CPU 192 is reduced basedon the control signal in other ways (for example, by driving a stopclock input of the CPU 192 directly with the throttle signal 181 outputby the throttle signal circuit 180). Where such closed-loop feedbackcontrol causes (when appropriate) the amount of current drawn by theportable computer 106 to be reduced such that load current output by thepower adapter 102 does not exceed the maximum current level for thepower adapter 102, the power adapter 102 is not current limited.

Because the control signal output by the power adapter 102 is indicativeof the total load current output by the power adapter 102 to all of thepowered devices 104 coupled to the power adapter 102, each of thepowered devices 104 need not include circuitry for measuring the amountof current used by the respective powered device 104 nor estimate orotherwise determine how much power the power adapter 102 is capable ofoutputting. Consequently, a powered device 104 can use the controlsignal output by the power adapter 102 to more precisely control theamount of power used by the powered device 104. Also, different poweradapters 102 that are capable of outputting different amounts of powercan be used to power the powered devices 104 while still having thepowered device 104 control how power is used.

The particular embodiment shown in FIG. 1 illustrates one example of howthe control signal output by the power adapter 102 can be used tocontrol the amount of power used by a powered device 104 such as aportable computer 106. In other embodiments and implementations, thecontrol signal output by the power adapter 102 is used in other ways tocontrol the amount of power used by a powered device 104. For example,in one such alternative embodiment, the control signal output by thepower adapter 102 is used by the portable computer 106 to control theamount of power that is used for battery charging (for example, by abattery charger included in the battery interface 108) in addition toand/or instead of controlling the amount of power used by the centralprocessing unit 192. In one exemplary implementation of such anembodiment, the battery charger compares the voltage developed acrossthe resistor 184 to a reference voltage. When the voltage across theresistor 184 is greater than the reference voltage, the battery chargerreduces the amount of power used by the battery charger for charging anybatteries coupled to the portable computer 106 (that is, the batterycharger is “throttled”). In such an exemplary implementation, the amountby which the battery charger reduces the power used for battery chargingis proportional to the amount by which the voltage across the resistor184 exceeds the reference voltage (until no power is used for batterycharging).

In one such implementation, the battery charger and/or the throttlesignal circuit 180 are configured so that when the control signal isbeing output by the power adapter 102 (which indicates that the amountof power used by the portable computer 106 should be reduced), theamount of power used for battery charging is reduced before thefrequency at which the CPU 192 operates is reduced. In some situations,by reducing the amount of power used for battery charging, the amount ofpower used by the portable computer 106 can be reduced enough to avoidthrottling the CPU 192. For example, in one such implementation, thethrottle signal circuit 180 is configured so that the sawtooth wave usedby the throttle signal circuit 180 has a DC offset that is greater thanthe reference voltage used by the battery charger. In such animplementation, when the voltage developed across the resistor 184 isgreater than the reference voltage used by the battery charger but isless than the DC offset of the sawtooth wave, the duty cycle of thethrottle signal 181 is zero percent. In such a situation, the batterycharger reduces the amount of power used for battery charging but theCPU 192 is not throttled.

Moreover, the particular embodiment shown in FIG. 1 illustrates oneexample of how the control signal can be generated by the power adapter102. In other embodiments and implementations, the control signal isgenerated by the power adapter 102 in other ways. For example, in theparticular embodiment shown in FIG. 1, the control signal circuit 164and the current limit feedback loop used to control the power supply 116make use of the same operational amplifier (that is, current sense opamp 146). In an alternative embodiment, separate operational amplifiers(or other comparators) are used in the control signal circuit 164 andthe current limit feedback loop used to control the power supply 116.

In the particular embodiment shown in FIG. 1, the control signal outputby the power adapter 102 is directly coupled to the powered device 104and is supplied to the portable computer 106 using the same interfaceused to supply power to the portable computer 106. In other embodimentsand implementations, the control signal output by the powered device 102is communicated to the powered device 104 in other ways. For example, inone embodiment, the control signal output by the power adapter 102 iscommunicated to the powered device 104 via one or more intermediarydevices (such as a docking station). One example of such an embodimentis shown in FIG. 2. Also, in other embodiments, the control signal iscommunicated to the portable computer 106 using an interface (forexample, a signal interface) other than the interface used to supplypower to the portable computer 106.

FIG. 2 is a block diagram of one embodiment of a computing system 200.In the embodiment shown in FIG. 2, the portable computer 106 of FIG. 1is inserted into or is otherwise coupled to a docking station 202 andthe portable computer 106, the docking station 202, and any devicescoupled to the portable computer 106 or the docking station 202 arepowered by the power adapter 102 of FIG. 1. The docking station 202, inthe embodiment shown in FIG. 2, includes an adapter interface 204 thatis used to couple the docking station 202 to the power adapter 102. Theadapter interface 204 of the docking station 202 comprises a pair ofpower terminals 206 that are used to receive power from the poweradapter 102 via the power terminals 160 of the power adapter's deviceinterface 114. In the particular embodiment shown in FIG. 2, the powerterminals 206 of the adapter interface 204 include an input voltageterminal and a ground terminal that are coupled to the output voltageterminal VOUT and the ground terminal GND, respectively, of the poweradapter's device interface 114. The adapter interface 204, in theembodiment shown in FIG. 2, comprises a control terminal 208 over whichinformation indicative of the amount of power output by the poweradapter 102 is received from the power adapter 102. In the embodimentshown in FIG. 2, the information indicative of the amount of poweroutput by the power adapter 102 comprises a control signal received fromthe power adapter 102 by the docking station 202 on the control terminal208 of the adapter interface 204.

The docking station 202 further comprises a device interface 212 (alsoreferred to here as the “portable computer interface” 212) that is usedto couple the docking station 202 to the portable computer 106. Theportable computer interface 212 comprises a pair of power terminals 214.In the embodiment shown in FIG. 2, the pair of power terminals 214comprises an output voltage terminal and a ground terminal. The outputvoltage terminal and the ground terminal of the portable computerinterface 212 of the docking station 202 are coupled to the inputvoltage terminal VADP and the ground terminal GND of the portablecomputer's adapter interface 174. In the embodiment shown in FIG. 2, thedevice interface 212 is shown as being coupled to the adapter interface174. The portable computer interface 212, in the embodiment shown inFIG. 2, further comprises a control terminal 216 over which informationindicative of the amount of power output by the power adapter 102received from the portable adapter 102 is supplied to the portablecomputer 106. In the embodiment shown in FIG. 2, the informationindicative of the amount of power output by the power adapter 102comprises a control signal received from the power adapter 102. Thecontrol signal is output by the docking station 202 on the controlterminal 216 to the portable computer 106. The control signal isindicative of the amount of power that is being output by the poweradapter 102 to the docking station 202. In this embodiment, the controlsignal is a function of the load current output by the power adapter102.

In the embodiment shown in FIG. 2, power received on the power terminals206 of the adapter interface 204 is used to power one or more components(for example, one or more light-emitting diodes) included in the dockingstation 202. Also, in the embodiment shown in FIG. 2, power received onthe power terminals 206 of the adapter interface 204 is used to powerthe portable computer 106 coupled to the docking station 202 and anynumber of other external devices (for example, external drive units suchas an external floppy, hard disk, CD, or DVD drive or external inputdevices such as external keyboards or pointing devices). In theembodiment shown in FIG. 2, the portable computer 106 is coupled to thepower terminals 206 in order to receive power from the power adapter 102and is coupled to the control terminal 208 in order to receive thecontrol signal from the power adapter 102. In the particular embodimentshown in FIG. 2, the docking station 202 passes the control signalthrough to the portable computer 106 on control signal line 209 withoutprocessing or otherwise using the control signal.

The portable computer 106 uses the control signal output by the poweradapter 102 to control the amount of power used by the portable computer106 in the manner described above in connection with FIG. 1. As notedabove, the control signal is generated by the power adapter 102 based onthe total load current output by the power adapter 102, which includesthe current used by all of the devices powered by the portable adapter102 (that is, the docking station 202, the portable computer 106, andany external devices).

The portable computer 106, by using the control signal, controls theamount of power used by the portable computer 106 based on the totalamount of power supplied by the power adapter 102 to all devices poweredby the power adapter 102. The control signal generated by the poweradapter 102 indicates to the portable computer 106 when the load currentoutput by the power adapter 102 exceeds the throttle current threshold,which indicates that the power adapter 102 is nearing the maximumcurrent level for the power adapter 102. The portable computer 106, inresponse to the control signal, throttles the CPU 194 or otherwisereduces the amount of power used by the portable computer 106. With suchan approach, the portable computer 106 need not itself measure how muchpower is being used by each of the devices powered by the power adapter102 or know how much power the power adapter 102 is capable ofoutputting.

In the particular embodiment shown in FIG. 2, the device interface 212is coupled to the adapter interface 174 of the power computer 106, whichis also used to couple the portable computer 106 directly to the poweradapter 102. In other embodiments and implementations, the portablecomputer 106 comprises a separate interface (for example, a “dockingstation interface”) for coupling the portable computer 106 to the deviceinterface 212 of the docking station 202.

FIG. 3 is a block diagram of one embodiment of a computing system 300.In the embodiment shown in FIG. 3, the portable computer 106 of FIG. 1is inserted into or is otherwise coupled to a docking station 302 andthe portable computer 106, the docking station 302, and any devicescoupled to the portable computer 106 or the docking station 302 arepowered by a power adapter 304.

The power adapter 304, in the embodiment shown in FIG. 3, is similar tothe power adapter 102 of FIG. 1 except that the power adapter 304 doesnot output a control signal (or other information indicative of theamount of power output by the power adapter 304) and does not include acontrol signal circuit 164 or a control terminal 162. That is, the poweradapter 304 comprises a device interface 350 that comprises a pair ofpower terminals 352 but does not include a control terminal over which acontrol signal is output. In the particular embodiment shown in FIG. 3,the power terminals 352 include an output voltage terminal VOUT and aground terminal GND. Otherwise, the power adapter 304 is similar to thepower adapter 102 of FIG. 1 and similar components are referenced inFIG. 3 using the same reference numerals used in FIG. 1 for thosecomponents.

The docking station 302, in the embodiment shown in FIG. 3, includes anadapter interface 306 that is used to couple the docking station 302 tothe power adapter 304. The adapter interface 306 of the docking station302 comprises a pair of power terminals 308 that are used to receivepower from the power adapter 304 via the power terminals 352 of thepower adapter's device interface 350. In the particular embodiment shownin FIG. 3, the power terminals 308 include an input voltage terminal anda ground terminal that are coupled to the output voltage terminal VOUTand the ground terminal GND, respectively, of the power adapter's deviceinterface 350. The adapter interface 306, in the embodiment shown inFIG. 3, comprises a control terminal 310 for receiving a control signal.However, as noted above, in the particular embodiment shown in FIG. 3,the power adapter 304 does not output a control signal. The controlterminal 310 of the adapter interface 306 can be used to receive acontrol signal from a different power adapter that outputs a controlsignal (for example, the portable adapter 102 of FIG. 1).

The docking station 302 further comprises a device interface 312 (alsoreferred to here as the “portable computer interface” 312) that is usedto couple the docking station 302 to the portable computer 106. Theportable computer interface 312 comprises a pair of power terminals 314.In the embodiment shown in FIG. 3, the pair of power terminals 314comprises an output voltage terminal and a ground terminal. The outputvoltage terminal and the ground terminal of the docking station'sportable computer interface 312 are coupled to the input voltageterminal VADP and the ground terminal GND of the portable computer'sadapter interface 174.

The docking station 302 generates information indicative of the amountof power received by the docking station 302 from the power adapter 304.In the embodiment shown in FIG. 3, the information indicative of theamount of power received by the docking station 302 from the poweradapter comprises a control signal that is a function of the loadcurrent received by the docking station 302 from the power adapter 304.The portable computer interface 312 further comprises a control terminal316 over which the control signal is output by the docking station 302to the portable computer 106. In other embodiments, the informationindicative of the amount of power received by the docking station 302from the power adapter 304 is communicated to the portable computer 106in other ways.

In the embodiment shown in FIG. 3, the docking station 302 comprises adocking station control signal circuit 318 that outputs the controlsignal. The docking station control signal circuit 318 outputs thecontrol signal when the load current received by the docking station 302exceeds a throttle current threshold. In the embodiment shown in FIG. 3,the docking station control signal circuit 312 does not output thecontrol signal when the load current received by the docking station 302is less than the throttle current threshold. In the embodiment shown inFIG. 3, the docking station 302 uses a predetermined throttle currentthreshold for any power adapter that is coupled to the docking station302, regardless of how much power any particular power adapter coupledto the docking station 302 is capable of outputting.

In the embodiment shown in FIG. 3, the docking station control signalcircuit 318 comprises a current sense resistor 320 coupled in seriesbetween the input voltage terminal of the adapter interface 306 and theoutput voltage terminal of the portable computer interface 312. One endof the current sense resistor 320 is coupled to the non-inverting inputof a current sense operational amplifier 322 (also referred to here asthe “docking station current sense op amp” 322). A reference voltage(also referred to here as “the docking station reference voltage”) iscoupled to the inverting input of the docking station current sense opamp 322. The docking station reference voltage is developed and coupledto the inverting input of the op amp 322 using a Zener diode 324 andappropriate bias resistors 326. The Zener diode 324 is coupled to thesupply voltage (VADP+4VDC) for the op amp 322 through a resistor 327. Acapacitor 328 is coupled between the inverting input and the output ofthe op amp 322 to provide control stability. The output of the dockingstation current sense op amp 322 is coupled via a resistor 330 to theemitter of a transistor 332. The base of the transistor 332 is coupledto the output voltage terminal 314 and the collector of the transistor332 is coupled to the anode of a diode 334. The cathode of the diode 334is coupled to the control terminal 316 of the portable computerinterface 312.

When the load current received by the docking station 302 from the poweradapter 304 is less than or equal to the throttle current threshold usedby the docking station 302, the output voltage of the docking stationcurrent sense op amp 322 is such that the voltage developed across theemitter and the base of the transistor 332 is insufficient to turn thetransistor 332 on. When the load current received by the docking station302 from the power adapter 304 is greater than the throttle currentthreshold used by the docking station 302, the output voltage of thedocking station current sense op amp 322 is such that the voltagedeveloped across the emitter and the base of the transistor 332 issufficient to turn the transistor 332 on. The current that flows fromthe emitter to the collector of the transmitter 332 is output on thecontrol terminal 316 as the control signal. In such an embodiment, thedocking station control signal circuit 318 is configured so that whenthe transistor 332 turns on, the current flowing from the emitter to thecollector of the transistor 332 (that is, the control signal) isproportional to the voltage output by the docking station current senseop amp 322, which is proportional to the amount by which the loadcurrent received by the docking station 302 from the power adapter 304exceeds the throttle current threshold for the docking station 304.

In the particular embodiment shown in FIG. 3, the control terminal 310of the adapter interface 306 is coupled to the control terminal 316 ofthe portable computer interface 312 over a control signal line 309(though in FIG. 3. the power adapter 304 does not include a controlterminal over which a control signal is output). In such an embodiment,the control signal output by the docking station control signal circuit318 is also coupled to the control terminal 316 of the portable computerinterface 312 over the control signal line 309.

The portable computer 106 uses the control signal output by the dockingstation 302 in order to control the amount of power used by the portablecomputer 106 in the manner described above in connection with FIG. 1.The portable computer 106, by using the control signal, controls theamount of power used by the portable computer 106 based on the totalamount of power received by docking station 302 from the power adapter304. However, the docking station 302, in the embodiment shown in FIG.3, uses the same throttle current threshold for all power adapters thatare coupled to the docking station 302, regardless of how much power anyparticular power adapter is actually capable of outputting. In otherwords, the docking station 302, in such an embodiment, assumes that allpower adapters are capable of outputting the same amount of power.

In the particular embodiment shown in FIG. 3, the device interface 312is coupled to the adapter interface 174 of the power computer 106, whichis also used to couple the portable computer 106 directly to the poweradapter 102. In other embodiments and implementations, the portablecomputer 106 comprises a separate interface (for example, a “dockingstation interface”) for coupling the portable computer 106 to the deviceinterface 312 of the docking station 302.

As noted above, the docking station 302 can be used with a power adapterthat outputs a control signal (for example, the power adapter 102 ofFIG. 1). FIG. 4 illustrates one such embodiment. FIG. 4 is a blockdiagram of one embodiment of a computing system 400. In the embodimentshown in FIG. 4, the portable computer 106 of FIG. 1 is inserted into oris otherwise coupled to the docking station 302 of FIG. 3 and theportable computer 106, the docking station 302, and any devices coupledto the portable computer 106 or the docking station 302 are powered bythe power adapter 102 of FIG. 1.

In the embodiment shown in FIG. 4, the control terminal 162 of the poweradapter's device interface 114 is coupled to the control terminal 310 ofthe docking station's adapter interface 306 and, as noted above, thecontrol terminal 310 of the adapter interface 306 is coupled to thecontrol terminal 316 of the docking station's portable computerinterface 312 over the control signal line 309. In such an embodiment,both the control signal circuit 164 of the power adapter 102 and thedocking station control signal circuit 318 of the docking station 302output a control signal if and when the respective throttle currentthreshold for each circuit is exceeded. The portable computer 106 usesany control signal received from the docking station 302 to control theamount of power used by the portable computer 106 in the mannerdescribed above in connection with FIG. 1.

In an implementation where the throttle current threshold for thedocking station control signal circuit 318 is lower than the controlsignal circuit 164 of the power adapter 102, the docking station controlsignal circuit 318 will output a control signal when the load currentreceived by the docking station 302 exceeds the throttle currentthreshold for that circuit 318, which causes the portable computer 106to reduce the amount of power it uses. Consequently, in such animplementation, the control signal circuit 164 of the power adapter 102typically will not output a control signal because the control signaloutput by the docking station control signal circuit 318 will typicallyprevent the load current output by the power adapter 102 from exceedingthe throttle current threshold for the power adapter 102.

In an implementation where the throttle current threshold for thecontrol signal circuit 164 of the power adapter 102 is lower than thedocking station control signal circuit 318, the control signal circuit164 of the power adapter 102 will output a control signal when the loadcurrent output by the power adapter 102 exceeds the throttle currentthreshold for the power adapter 102, which causes the portable computer106 to reduce the amount of power it uses. Consequently, in such animplementation, the docking station control signal circuit 318 typicallywill not output a control signal because the control signal output bythe control signal circuit 164 of the power adapter will typicallyprevent the load current received by the docking station 302 fromexceeding the throttle current threshold for the docking station controlsignal circuit 318. In other embodiments and implementations, thethrottle current threshold for the control signal circuit 164 of thepower adapter 102 is the same as the throttle current threshold for thedocking station control signal circuit 318 or the throttle currentthreshold for the control signal circuit 164 of the power adapter 102 ishigher than the throttle current threshold for the docking stationcontrol signal circuit 318.

In other embodiments, a control terminal included in a device interfaceof a power adapter on which a control signal (or other informationindicative of an amount of load current output by a power adapter) maybe output is used for identifying one or more attributes of the poweradapter. For example, in one such embodiment, the control terminal isused by a powered device coupled to the power adapter to determine ifthe power rating of the power adapter is equal to or greater than thepower rating of the powered device (that is, the minimum amount of powerrequired by the powered device). FIG. 5 illustrates one such embodiment.

FIG. 5 is a high-level block diagram of one embodiment of a computingsystem 500. The computing system 500 comprises a power adapter 502 thatis used to power at least one powered device 504. In the particularembodiment shown in FIG. 5, the powered device 504 comprises a portablecomputer 506. The portable computer 506, in the embodiment shown in FIG.5, can be powered by the power adapter 502 (when coupled thereto) or bya battery coupled to the portable computer 506 via a battery interface508. In other embodiments, one or more other external devices that arecommunicatively coupled to the portable computer 506 (for example, adocking station or an external drive unit such as a CD, DVD, or floppydrive unit) are also powered by the power adapter 502. In some otherembodiments, a power adapter is used to power other types of electronicdevices such as other types of battery-powered devices.

The power adapter 502 comprises a power-source interface 510 that isused to couple the power adapter 502 to an AC power source 512 (such asan AC outlet). The power adapter 502 also comprises a device interface514 that is used to couple the power adapter 502 to the powered device504 (the portable computer 506 in the embodiment shown in FIG. 5). Inone implementation of the embodiment shown in FIG. 5, the power adapter502 is directly coupled to the power source 512 and to the portablecomputer 506 using appropriate cabling and connectors. In anotherembodiment, the power adapter 502 is coupled to the portable computer506 indirectly via one or more intermediary devices such as a dockingstation.

The power adapter 502 also comprises a power supply 516 that converts anAC line voltage from the AC power source 512 to a lower DC voltagesuitable for use by the portable computer 506. In the embodiment shownin FIG. 5, the power supply 516 is designed to output a particularnominal output voltage on the device interface 514 for use by theportable computer 506. The power supply 516 comprises any suitable powersupply topology now known or later developed. In the embodiment shown inFIG. 5, the power supply 516 comprises a controller 518 that controlsthe voltage output by the power supply 516 (for example, based on thevoltage and/or load current output by the power adapter 502).

The device interface 514 of the power adapter 502 comprises a pair ofpower terminals 560 that are used to provide power to the portablecomputer 506. In the particular embodiment shown in FIG. 5, the powerterminals 560 include an output voltage terminal (VOUT) and a groundterminal (GND). The device interface 514 further comprises a controlterminal 562. In the embodiment shown in FIG. 5, the control terminal562 is coupled to VOUT via a pull-up resistor 595 (also referred to hereas “resistor Radp” or just “Radp”).

At least one of the powered devices 504 powered by the power adapter 502comprises an adapter interface that is used to couple the powered device504 to the power adapter 502. In the embodiment shown in FIG. 5, theportable computer 506 comprises an adapter interface 574. The adapterinterface 574 comprises a pair of power terminals 576 that are used toreceive power from the power adapter 502 via the power terminals 560 ofthe power adapter's device interface 514. In the particular embodimentshown in FIG. 5, the power terminals 576 include an input voltageterminal (VADP) and a ground terminal (GND) that are coupled to theoutput voltage terminal VOUT and the ground terminal GND, respectively,of the power adapter's device interface 514.

The adapter interface 574 further comprises a control terminal 578 thatis coupled to the control terminal 562 of the device interface 514 ofthe power adapter 502 when the power adapter 502 is coupled to theportable computer 506. The control terminal 578 of the portable computer506 is used as an input to an identification circuit 580 that identifiesone or more attributes of any power adapter 502 coupled to the portablecomputer 506. In the particular embodiment shown in FIG. 5, theidentification circuit 580 identifies whether the power adapter 502 hasa power rating that is greater than or equal to a particular “full-powerpower rating” associated with the portable computer 506. In such anembodiment, the full-power power rating is the amount of power needed bythe portable computer 506 to be operated in a full-power mode. In oneimplementation of such an embodiment, the full-power mode is a mode inwhich the portable computer 506 is operated without degrading theperformance of the portable computer 506 (for example, without reducingclock frequency at which a CPU is operated). In another implementation,the full-power mode is an operational mode in which a user is able touse the portable computer 506 (as opposed to a sleep mode in whichbattery charging occurs but the user is not otherwise able to use theportable computer 506).

In the embodiment shown in FIG. 5, the identification circuit 580comprises a pull-down resistor 596 (also referred to here as “resistorRnotebook” or just “Rnotebook”) that couples the control terminal 578 toground. When the power adapter 502 is coupled to the portable computer506, the pull-up resistor 595 of the power adapter 502 and the pull-downresistor 596 of the portable computer 506 form a voltage divider. Thevoltage developed at the node formed between the pull-up resistor 595and the pull-down resistor 596 (that is, at the control terminal 578) isused by the identification circuit 580 to determine if the power ratingof the power adapter 502 is equal to or greater than the full-powerpower rating of the portable computer 506.

In the embodiment shown in FIG. 5, the portable computer 506 furthercomprises a comparator 597 that compares the voltage developed at thecontrol terminal 578 to a reference voltage. The voltage developed atthe control terminal 578 (that is, the voltage developed at the nodeformed between the pull-up resistor 595 and the pull-down resistor 596)is coupled to the non-inverting input of the comparator 597 and thereference voltage is coupled to the inverting input of the comparator597. The voltage developed at the control terminal 578 is indicative ofthe ratio of the resistance value of Radp and the resistance value ofRnotebook. In the particular embodiment shown in FIG. 5, the referencevoltage is developed at a node formed between a first bias resistor 531and a second bias resistor 598. The first and second bias resistors 531and 598 are coupled in series between VADP and ground. The voltagedeveloped at the node between the first and second bias resistors 531and 598 (that is, the reference voltage) is indicative of the ratio ofthe resistance value of the first resistor 531 and the resistance valueof the second resistor 598. The output voltage of the comparator 597 iscoupled to a logic voltage level (VDD) via a resistor 599. The outputvoltage of the comparator 597 is indicative of the difference betweenthe voltage developed at the control terminal 578 and the referencevoltage. With such an approach, variations in VADP are “cancelled” outof the comparison performed by the comparator 597.

In one exemplary implementation of such an embodiment, the biasresistors 598 are configured so that the reference voltage is just underone-half of VADP. In such an implementation, if the pull-up resistor 595of the power adapter 502 is less than or equal to the pull-down resistor596 of the portable computer 506, the comparator 597 outputs a logic“high” signal. If the pull-up resistor 595 of the power adapter 502 isgreater than the pull-down resistor 596 of the portable computer 506,the comparator 597 outputs a logic “low” signal. In such animplementation, the pull-up resistor 595 of the power adapter 502 andthe pull-down resistor 596 of the portable computer 506 are selected sothat the pull-up resistor 595 is less than or equal to the pull-downresistor 596 of the portable computer 506 if the power rating of thepower adapter 502 is equal to or greater than the full-power powerrating of the portable computer 506, and that the pull-up resistor 595of the power adapter 502 is greater than the pull-down resistor 596 ofthe portable computer 506 if the power rating of the power adapter 502is less than the full-power power rating of the portable computer 506.

In the particular embodiment of FIG. 5, the portable computer 506further comprises an embedded controller 582 to which the output of thecomparator 597 is output. In such an embodiment, when the power adapter502 is initially coupled to the portable computer 506, the embeddedcontroller 582 detects that fact (for example, because power is beingsupplied on the adapter interface 574 of the portable computer 506) andchecks the output of the comparator 597. In the exemplary implementationdescribed in the previous paragraph, if the output of the comparator 597has a logic high value, the embedded controller 582 learns that thepower rating of the power adapter 502 is equal to or greater than thepower rating of the portable computer 506. If the output of thecomparator 597 has a logic low value, the embedded controller 582 learnsthat the power rating of the power adapter 502 is less than the powerrating of the portable computer 506. In one such implementation, whenthe embedded controller 582 learns that the power rating of the poweradapter 502 is greater than or equal to the power rating of the portablecomputer 506, the embedded controller 582 operates the portable computer506 in a “full-power mode.” When the embedded controller 582 learns thatthe power rating of the power adapter 502 is less than the power ratingof the portable computer 506, the embedded controller 582 does not allowthe portable computer 506 to operate in the full-power mode and,instead, operates the portable computer 506 in a “low-power mode” (forexample, where a CPU included in the portable computer 506 is operatedat a lower clock frequency). In one such implementation, the embeddedcontroller 582 notifies a user of the portable computer 506 that theportable computer 506 is operating in low-power mode. In otherembodiments and implementations, other actions are taken in the eventthat the portable computer 506 learns that the power rating of the poweradapter 502 is less than the full-power power rating of the portablecomputer 506. For example, in one such other implementation, when theembedded controller 582 learns that the power rating of a power adapter502 is less than the full-power power rating of the portable computer506, the embedded controller 582 may operate the portable computer 506in a sleep mode in which battery charging occurs but a user is nototherwise able to use the portable computer 506. In one example of suchan implementation, the power adapter 502 comprises a small “travel”adapter that has a power rating sufficient for battery charging but notsufficient for the portable computer 506 to operate in full-power mode.

FIG. 6 is a chart 600 illustrating exemplary values of Radp andRnotebook for various power ratings in one implementation of the system500 of FIG. 5. Each row of the chart 600 corresponds to a given powerrating in Watts. The column labeled Radp in chart 600, for each row ofthe chart 600, contains a resistor value (in Kiloohms) for resistor Radpthat is associated with a power adapter 502 having the power ratingassociated with that row. The column labeled Rnotebook in chart 600, foreach row of the chart 600, contains a resistor value for resistorRnotebook that is associated with a portable computer 506 having thefull-power power rating associated with that row. In the particularexample shown in chart 600, the resistor values are configured for areference voltage that is thirty percent of VADP.

For example, in one implementation designed in accordance with chart600, a first power adapter 502 having a power rating of 65 Wattscomprises a 383 Kiloohm pull-up resistor 595 (Radp), a second poweradapter 502 having a power rating of 50 Watts comprises a 499 Kiloohmpull-up resistor 595 (Radp), and a portable computer 506 having afull-power power rating of 65 Watts comprises a 191 Kiloohm pull-downresistor 596 (Rnotebook). If the first power adapter 502 (with a Radphaving a resistance of 383 Kiloohms) is coupled to the portable computer506 (with a Rnotebook having a resistance of 191 Kiloohms), thecomparator 597 of the portable computer 506 outputs a logic high valueindicating that the power rating of that power adapter 502 is equal toor greater than the full-power power rating of the portable computer506. If the second power adapter 502 (with a Radp having a resistance of499 Kiloohms) is coupled to the portable computer 506 (with a Rnotebookhaving a resistance of 191 Kiloohms), the comparator 597 of the portablecomputer 506 outputs a logic low value indicating that the power ratingof that power adapter 502 is less than the full-power power rating ofthe portable computer 506. In the latter situation, the embeddedcontroller 582 of the portable computer 506, for example, could operatethe portable computer 506 in a low-power mode.

FIG. 7 is a chart 700 illustrating the voltage difference between thetwo inputs of the comparator 597 of a portable computer 506 implementedusing chart 600 of FIG. 6 when a power adapter 502 implemented usingchart 600 of FIG. 6 is directly coupled to the portable computer 506.Each row of the chart 700 corresponds to a power adapter 502 comprisinga pull-up resistor 595 having a resistance value from the intersectionof the respective row and column of chart 600. Each column of the chart700 corresponds to a portable computer 506 comprising a pull-downresistor 596 having a resistance value from the intersection of therespective row and column of chart 600. For example, in such animplementation, where a power adapter 502 having a power rating of 50Watts (with a Radp having a resistance of 499 Kiloohms) is coupled to aportable computer 106 having a full-power power rating of 65 Watts (witha Rnotebook having a resistance of 191 Kiloohms), the voltage differencebetween the two inputs of the comparator 597 of the portable computer506 is −0.54 Volts, which results in the comparator 597 outputting alogic low value.

The power adapter 502 is shown in FIG. 5 as being directly coupled tothe portable computer 506. In other usage scenarios, the power adapter502 is coupled to the portable computer 506 via one or more intermediarydevices such as a docking station. In some embodiments, such anintermediary device consumes at least a portion of the power supplied bythe power adapter 502. FIG. 8 illustrates one such usage scenario.

FIG. 8 is a block diagram of one embodiment of a computing system 800.In the embodiment shown in FIG. 8, the portable computer 506 of FIG. 5is inserted into or is otherwise coupled to a docking station 802 andthe portable computer 506, the docking station 802, and any devicescoupled to the portable computer 506 or the docking station 802 arepowered by the power adapter 502 of FIG. 5. The docking station 802, inthe embodiment shown in FIG. 8, includes an adapter interface 804 thatis used to couple the docking station 802 to the power adapter 502. Theadapter interface 804 of the docking station 802 comprises a pair ofpower terminals 806 that are used to receive power from the poweradapter 502 via the power terminals 560 of the power adapter's deviceinterface 514. In the particular embodiment shown in FIG. 8, the powerterminals 806 of the adapter interface 804 include an input voltageterminal and a ground terminal that are coupled to the output voltageterminal VOUT and the ground terminal GND, respectively, of the poweradapter's device interface 514. The adapter interface 804, in theembodiment shown in FIG. 8, comprises a control terminal 808 that iscoupled to the control terminal 562 of the power adapter 502 when thedocking station 802 is coupled to the power adapter 502.

The docking station 802 further comprises a device interface 812 (alsoreferred to here as the “portable computer interface” 812) that is usedto couple the docking station 802 to the portable computer 506. Theportable computer interface 812 comprises a pair of power terminals 814.In the embodiment shown in FIG. 8, the pair of power terminals 814comprises an output voltage terminal and a ground terminal. The outputvoltage terminal and the ground terminal of the portable computerinterface 812 of the docking station 802 are coupled to the inputvoltage terminal VADP and the ground terminal GND of the portablecomputer's adapter interface 574. In the embodiment shown in FIG. 8, thedevice interface 812 is shown as being coupled to the adapter interface574. The portable computer interface 812, in the embodiment shown inFIG. 8, further comprises a control terminal 816 that is coupled to thecontrol terminal 578 of the portable computer 506 when the dockingstation 802 is coupled to the portable computer 506.

In the embodiment shown in FIG. 8, power received on the power terminals806 of the adapter interface 804 is used to power one or more components803 (for example, one or more light-emitting diodes) included in thedocking station 802. Also, in the embodiment shown in FIG. 8, powerreceived on the power terminals 806 of the adapter interface 804 is usedto power the portable computer 506 coupled to the docking station 802and any number of other external devices (for example, external driveunits such as an external floppy, hard disk, CD, or DVD drive orexternal input devices such as external keyboards or pointing devices).

In the embodiment shown in FIG. 8, the control terminal 808 of theadapter interface 804 is coupled to the control terminal 816 of theportable computer interface 816 via a Zener diode 820. When the poweradapter 502 is coupled to the adapter interface 804 of the dockingstation 802 and the portable computer 506 is coupled to the portablecomputer interface 812 of the docking station 802, the control terminal562 of the power adapter 502 is coupled to the control terminal 578 ofthe portable computer 506 via the Zener diode 820 of the docking station802. The Zener diode 820 provides a fixed voltage drop (for example, 3Volts) from the control terminal 808 of the adapter interface 804 to thecontrol terminal 816 of the portable computer interface 812. As result,the voltage developed at the node formed between the pull-up resistor595 and the pull-down resistor 596 is lower than the voltage developedat the node formed between the pull-up resistor 595 and the pull-downresistor 596 when the power adapter 502 is directly coupled to theportable computer 506. In other embodiments and implementations, a fixedvoltage drop is provided from the control terminal 808 of the adapterinterface 804 to the control terminal 816 of the portable computerinterface 812 in other ways (for example, using a two-terminal referencevoltage integrated circuit).

In one implementation of such an embodiment implemented using the chart600 of FIG. 6, the system 800 is configured so that when the poweradapter 502 is coupled to the adapter interface 804 of the dockingstation 802 and the portable computer 506 is coupled to the portablecomputer interface 812 of the docking station 802, the voltage dropcaused by the Zener diode 820 is sufficient to cause the power adapter502 to appear to the portable computer 506 as a power adapter having thenext lowest power rating in chart 600. For example, when a power adapter502 having a power rating of 135 Watts (and comprising a pull-upresistor 595 having a resistance of 169 Kiloohms) is coupled to thedocking station 802; the power adapter 502 appears to a portablecomputer 506 coupled to the docking station 802 as a power adapterhaving a power rating of 120 Watts due to the voltage drop caused by theZener diode 820. In this way, the amount of power consumed by thedocking station 802 is taken into account by the portable computer 506when determining if the power adapter 502 is able to provide enoughpower to operate the portable computer 506 in full-power mode.

FIG. 9 is a chart 900 illustrating the voltage difference between thetwo inputs of the comparator 597 of a portable computer 506 implementedusing chart 600 of FIG. 6 when a power adapter 502 implemented usingchart 600 of FIG. 6 is coupled to the portable computer 506 via thedocking station 802 of FIG. 8.

In the embodiment shown in FIG. 5, the portable computer 506 isconfigured to compare the voltage developed at the control terminal 578to one reference voltage. In other embodiments, the voltage developed atthe control terminal 578 is compared to multiple references voltages.FIG. 10 illustrates one such embodiment.

FIG. 10 is a block diagram of one embodiment of a computing system 1000.In the embodiment shown in FIG. 10, the power adapter 502 of FIG. 5 iscoupled to a portable computer 1006. The portable computer 1006 of FIG.10 is similar to the portable computer 506 of FIG. 5 and similarcomponents are referenced in FIG. 10 using the same reference numeralsused in FIG. 5 for those components.

The portable computer 1006 of FIG. 10 comprises a first comparator 1004that compares the voltage developed at the control terminal 578 to afirst reference voltage. The portable computer 1006 further comprises asecond comparator 1005 that compares the voltage developed at thecontrol terminal 578 to a second reference voltage. In such anembodiment, the first reference voltage is indicative of a particular“full-power” power rating associated with the portable computer 1006. Insuch an embodiment, the full-power power rating is the amount of powerneeded by the portable computer 1006 to be operated in a full-powermode. The voltage developed at the control terminal 578 is coupled tothe non-inverting input of the first comparator 1004 and the firstreference voltage is coupled to the inverting input of the firstcomparator 1004. In such an embodiment, the second reference voltage isindicative of a particular “minimum” power rating associated with theportable computer 1006. In such an embodiment, the minimum power ratingis the minimum amount of power needed by the portable computer 1006 tobe operated in a low-power mode. The voltage developed at the controlterminal 578 is coupled to the non-inverting input of the secondcomparator 1005 and the second reference voltage is coupled to theinverting input of the second comparator 1005.

The portable computer 1006 comprises a first, second, and thirdresistors 1008, 1010, and 1012, respectively that are coupled in seriesbetween VADP and ground. The first reference voltage is developed at thenode between the first and second resistors 1008 and 1010 and the secondreference voltage is developed at the node between the second and thirdresistors 1010 and 1012. The output voltage of the first comparator 1004is coupled to a logic voltage level (VDD) via a resistor 1014. Theoutput voltage of the first comparator 1004 is indicative of thedifference between the voltage developed at the control terminal 578 andthe first reference voltage. The output voltage of the second comparator1005 is coupled to a logic voltage level (VDD) via a resistor 1016. Theoutput voltage of the second comparator 1005 is indicative of thedifference between the voltage developed at the control terminal 578 andthe second reference voltage.

In the embodiment shown in FIG. 10, the system 1000 is configured sothat when a power adapter 502 having a power rating that is less thanthe minimum power rating associated with the second reference voltage(and a pull-up resistor 595 having an corresponding resistance value) iscoupled to the portable computer 1006, both the first and secondcomparators 1004 and 1005 output a logic low value. Moreover, the system1000 is configured so that when a power adapter 502 having a powerrating that is greater than or equal to the minimum power ratingassociated with the second reference voltage but less than thefull-power power rating associated with the first reference voltage iscoupled to the portable computer 1006, the first comparator 1004 outputsa logic low value and the second comparator 1005 outputs a logic highvalue. In such an embodiment, the system 1000 is configured so that whena power adapter 502 having a power rating that is greater than or equalto the maximum power rating associated with the first reference voltageis coupled to the portable computer 1006, both the comparators 1004 and1005 output a logic high value.

In the particular embodiment of FIG. 10, the portable computer 1006further comprises an embedded controller 1082 to which the output of thefirst and second comparators 1004 and 1005 are output. In such anembodiment, when the power adapter 502 is initially coupled to theportable computer 1006, the embedded controller 1082 detects that fact(for example, because power is being supplied on the adapter interface574 of the portable computer 1006) and checks the outputs of the firstand second comparators 1004 and 1005. In the embodiment shown in FIG.10, if both comparators 1004 and 1005 output a logic high value, theembedded controller 1082 learns that the power rating of the poweradapter 502 is equal to or greater than the full-power power ratingassociated with the portable computer 1006. In such a situation, theembedded controller 1082 operates the portable computer 1006 in thefull-power mode.

If the first comparator 1004 outputs a logic low value but the secondcomparator 1005 outputs a logic high value, the embedded controller 1082learns that the power rating of the power adapter 502 is equal to orgreater than the minimum power rating associated with the portablecomputer 1006 but is less than the full-power power rating associatedwith portable computer 1006. In such a situation, the embeddedcontroller 1082 may operate the portable computer 1006 in a low-powermode (for example, where a CPU included in the portable computer 1006 isoperated at a lower clock frequency).

If both the comparators 1004 and 1005 output a logic low value, theembedded controller 1082 learns that the power rating of the poweradapter 502 is less than the minimum-power power rating associated withthe portable computer 1006. In such a situation, the embedded controller1082 may power off the portable computer 1006 (for example, by havingthe portable computer 1006 enter a “sleep” state in which batterycharging occurs but the user is not otherwise able to use the portablecomputer 1006).

FIG. 11 is a block diagram of one embodiment of a computing system 1100.In the embodiment shown in FIG. 11, a power adapter 1102 is directlycoupled to the portable computer 1106 (though in other embodiments, thepower adapter 1102 is coupled to the portable computer 1106 via one ormore intermediary devices such as the docking station 802 of FIG. 8).Except as described here, the power adapter 1102 and the portablecomputer 1106 are similar to the power adapter 102 and portable computer106 of FIG. 1, respectively, and similar components are referenced inFIG. 11 using the same reference numerals used in FIG. 1 for thosecomponents. The power adapter 1102 comprises a pull-up resistor 1195(also referred to here as “resistor Radp” or just “Radp”) coupled acrossVOUT and the control terminal 162 of the adapter interface 114 of thepower adapter 1102 in parallel with the control signal circuit 164. Thepull-up resistor 1195 of the power adapter 1102, in the embodiment shownin FIG. 11, has a resistance value that is much larger than the resistor184 used in the throttle signal circuit 180 of the portable computer1106 to couple the control signal 178 to ground. In one implementationof such an embodiment, the resistor 184 has a resistance value of 2Kiloohms and the pull-up resistor 1195 has a resistance value that ismuch larger than 2 Kiloohms.

In the embodiment shown in FIG. 11, the portable computer 1106 comprisesboth the throttle signal circuit 180 and an identification circuit 580similar to the identification circuit 580 of FIG. 5 (and similarcomponents are referenced in FIG. 11 using the same reference numeralsused in FIG. 5 for such components). In such an embodiment, thenon-inverting input of the comparator 186 of the throttle signal circuit180 is coupled to the control terminal 178 of the portable computer 1106using a Zener diode 101 having a voltage drop of, for example, 6.8Volts. Also, in such an embodiment, the sawtooth wave used by thethrottle signal circuit 180 has a DC offset (for example, a sawtoothwave having a 1.0 Volt DC offset and a maximum amplitude of 2.0 Volts).When the power adapter 1102 is coupled to the portable computer 1106, atfirst, the control signal output by the control signal circuit 164 ofthe power adapter 1102 is zero. Because the pull-up resistor 1195 ismuch larger than the resistor 184, the current through the pull-upresistor 1195 will be insufficient to generate current on the controlterminal 178 sufficient to “turn on” the throttle signal circuit 180.The Zener diode 1101 used to couple the throttle signal circuit 180 tothe control terminal 178 of the portable computer 1106 does not affectthe identification circuit 580 since the voltage developed at thecontrol terminal 178 is well less than the Zener voltage of the Zenerdiode 1101.

In such an embodiment, the output of the identification circuit 580 ischecked by an embedded controller 1182 of the portable computer 1106when the power adapter 1102 is first coupled to the portable computer1106. The control signal circuit 164 of the power adapter 1102 typicallydoes not output the control signal during this time because the loadcurrent output by the power adapter 1102 typically does not rise abovethe throttle current threshold during this time or because the responsetime of the control signal circuit 164 is long enough that the controlsignal circuit 164 will not react (and output a control signal) duringthis time. After the embedded controller 1182 of the portable computer1106 reads the output of the identification circuit 580 (and determineswhether or not to operate the portable computer in full-power mode asdescribed above in connection FIG. 5), the embedded controller 1182 neednot read the output of the identification circuit 580 again while thesame power adapter 1102 is coupled to the portable computer 1106.Thereafter, the amount of power used by the portable computer 1106 maybe controlled using information indicative of the amount of power outputby the power adapter 1102 (that is, using the control signal output bythe control signal circuit 164) as described above in connection withFIG. 1.

In other embodiments, a control terminal included in a device interfaceof a power adapter on which a control signal (or other informationindicative of the amount of load current output by a power adapter) maybe output is used for identifying one or more attributes of the poweradapter in other ways. FIG. 12 illustrates one such embodiment.

FIG. 12 is a block diagram of one embodiment of a computing system 1200.The computing system 1200 comprises a power adapter 1202 that is used topower at least one powered device 1204. In the particular embodimentshown in FIG. 12, the powered device 1204 comprises a portable computer1206. The portable computer 1206, in the embodiment shown in FIG. 12,can be powered by the power adapter 1202 (when coupled thereto) or by abattery coupled to the portable computer 1206 via a battery interface1208. In other embodiments, one or more other external devices that arecommunicatively coupled to the portable computer 1206 (for example, adocking station or an external drive unit such as a CD, DVD, or floppydrive unit) are also powered by the power adapter 1202. In some otherembodiments, a power adapter is used to power other types of electronicdevices such as other types of battery-powered devices.

Except as described here, the power adapter 1202 is similar to the poweradapter 502 of FIG. 5 and similar components are referenced in FIG. 12using the same reference numerals used in FIG. 5 for those components.In the embodiment shown in FIG. 12, the resistor Radp is selected sothat the resistance value of resistor Radp is indicative of the powerrating of the power adapter 1202. In one exemplary implementation ofsuch an embodiment, a set of power adapters 1202 having respective powerratings of 50 Watts, 65 Watts, 90 Watts, and 120 Watts compriserespective resistors Radp having resistance values of, for example, 50Kiloohms, 75 Kiloohms, 100 Kiloohms, and 125 Kiloohms, respectively.That is, a power adapter 1202 having a power rating of 90 Watts, forexample, has a resistor Radp having a resistance value of 100 Kiloohms.In other embodiments and implementations, other component values areused.

At least one of the powered devices 1204 powered by the power adapter1202 comprises an adapter interface that is used to couple the powereddevice 1204 to the power adapter 1202. In the embodiment shown in FIG.12, the portable computer 1206 comprises an adapter interface 1274. Theadapter interface 1274 comprises a pair of power terminals 1276 that areused to receive power from the power adapter 1202 via the powerterminals 560 of the power adapter's device interface 514. In theparticular embodiment shown in FIG. 12, the power terminals 1276 includean input voltage terminal (VADP) and a ground terminal (GND) that arecoupled to the output voltage terminal VOUT and the ground terminal GND,respectively, of the power adapter's device interface 514.

The adapter interface 1274 further comprises a control terminal 1278that is coupled to the control terminal 562 of the device interface 514of the power adapter 1202 when the power adapter 1202 is coupled to theportable device 1206. The control terminal 1278 of the portable computer1206 is used as an input to an identification circuit 1280 thatidentifies one or more attributes of the power adapter 1202 coupled tothe portable computer 1206. In the particular embodiment shown in FIG.12, the identification circuit 1280 is used to identify a power ratingassociated with any power adapter 1202 coupled to the portable computer1206. The identification circuit 1280 comprises a capacitor 1230. In oneimplementation of such an embodiment, the capacitor 1230 has acapacitance of 0.1 microfarads. The capacitor 1230 has a first terminalthat is coupled to ground. The capacitor 1230 has a second terminal thatis coupled to the control terminal 1278 of the portable computer 1206via first transistor switch 1232. When the power adapter 1202 is coupledto the portable computer 1206, the control terminal 1278 is coupled tothe control terminal 562 of the power adapter 1202, which in turncouples the capacitor 1230 to VOUT via the resistor Radp of the poweradapter 1202. The second terminal of the capacitor 1230 is also coupledto VADP of the portable computer 1206 via a second transistor switch1234 and a pull-up resistor 1236 (also referred to here as “resistorRnotebook” or just “Rnotebook”). In one implementation, the first andsecond transistors 1232 and 1234 are implemented using respective BSS138field-effect transistors.

The identification circuit 1280 is coupled to an embedded controller1282. In the particular embodiment shown in FIG. 12, the embeddedcontroller 1282 comprises an input/output terminal GPIO_1 and an outputterminal GPO_2. The input/output terminal GPIO_1 of the embeddedcontroller 1282 is coupled to the second terminal of the capacitor 1230via a resistor 1238. In one implementation of such an embodiment, theresistor 1238 has a resistance value of 220 Ohms. The output terminalGPO_2 of the embedded controller 1282 is used to selectively couple thesecond terminal of the capacitor 1230 to VADP either via Radp of thepower adapter 1202 by closing the first transistor 1232 (while thesecond transistor 1234 is open) or via Rnotebook of the portablecomputer 1206 by closing the second transistor 1234 (while the firsttransistor 1232 is open). In the embodiment shown in FIG. 12, the secondtransistor 1234 is closed (which electrically couples the secondterminal of the capacitor 1230 to VADP via Rnotebook) and the firsttransistor 1232 is open (which electrically decouples the secondterminal of the capacitor 1230 from Radp) when a “low” value is outputby the embedded controller 1280 on the output terminal GPO_2. The gateof the second transistor 1234 is coupled to the output terminal GPO_2 ofthe embedded controller 1282 via a first inverting amplifier 1239 thatamplifies the low signal output by the embedded controller 1282 on theoutput terminal GPO_2 to a suitable voltage (for example, 5 Volts) toturn on the second transistor 1234. The gate of the first transistor1232 is coupled to the output of the first inverting amplifier 1239 viasecond inverting amplifier 1240. When the output of the output terminalGPO_2 is low, the second inverting amplifier 1240 applies an appropriatelow-voltage value to the gate of the first transistor 1232 to open thefirst transistor 1232.

In the embodiment shown in FIG. 12, the second transistor 1234 is open(which electrically decouples the second terminal of the capacitor 1230from Rnotebook) and the first transistor 1232 is closed (whichelectrically couples the second terminal of the capacitor 1230 to VADPvia Radp) when a “high” value is output by the embedded controller 1280on the output terminal GPO_2. In such a situation, the first invertingamplifier 1239 applies an appropriate low-voltage value to the gate ofthe second transistor 1234 to open the second transistor 1234 and thesecond inverting amplifier 1239 applies an appropriate high-voltagevalue to the gate of the first transistor 1232 to close the firsttransistor 1232.

The embedded controller 1282, in the embodiment shown in FIG. 12, runsan identification routine when the power adapter 1202 is first coupledto the portable computer 1206. The identification routine, in oneimplementation, comprises appropriate program instructions that arestored (or otherwise embodied) on an appropriate storage medium fromwhich at least a portion of the program instructions are read by theembedded controller 1282 for execution thereby. When the power adapter1202 is first coupled to the portable computer 1206, the embeddedcontroller 1282 causes a low value to be output on the output terminalGPO_2, which closes the second transistor 1234 and opens the firsttransistor 1232. Closing the second transistor 1234 electrically couplesthe second terminal of the capacitor 1230 to VADP via resistorRnotebook. During this time, the embedded controller 1282 outputs a lowvalue on the input/output terminal GPIO_1, which causes the capacitor1230 to be discharged through resistor 1238. After the capacitor 1230has been fully discharged, the input/output terminal GPIO_1 isconfigured as an input, which causes the current flowing throughRnotebook charges the capacitor 1230. The embedded controller 1282monitors the voltage at the input/output terminal GPIO_1 to determinehow long (for example, using a timer and/or a counter) it takes for thevoltage at the input/output terminal GPIO_1 to reach a logic high value(for example, 2.3 Volts). How long it takes for the voltage at theinput/output terminal GPIO_1 to reach a logic high value is alsoreferred to here as time Tnbk. The embedded controller 1282 saves thetime Tnbk.

The embedded controller 1282 controller then causes a high value to beoutput on the output terminal GPO_2, which opens the second transistorswitch 1234 and closes the first transistor 1232. Closing the firsttransistor switch 1232 electrically couples the second terminal of thecapacitor 1230 to VADP via the resistor Radp. During this time, theembedded controller 1282 outputs a low value on the input/outputterminal GPIO_1, which causes the capacitor 1230 to be dischargedthrough resistor 1238. After the capacitor 1230 has been fullydischarged, the input/output terminal GPIO_1 is configured as an input,which causes the current flowing through Radp charges the capacitor1230. The embedded controller 1282 monitors the voltage at theinput/output terminal GPIO_1 to determine bow long (for example, using atimer and/or a counter) it takes for the voltage at the input/outputterminal GPIO_1 to reach a logic high value (for example, 2.3 Volts).How long it takes for the voltage at the input/output terminal GPIO_1 toreach a logic high value is also referred to here as time Tadp. Theembedded controller 1282 saves the time Tadp.

The embedded controller 1282, in the embodiment shown in FIG. 12,calculates a ratio of Tadp/Tnbk and uses that ratio Tadp/Tnbk toidentify (or otherwise characterize) the power rating of the poweradapter 1202. For example, in one implementation, the embeddedcontroller 1282 uses a lookup table in which various Tadp/Tnbk ratiosare stored. Each stored Tadp/Tnbk ratio is associated with a poweradapter 1202 having a particular power rating. In such animplementation, the embedded controller 1282 compares the measuredTadp/Tnbk ratio to the Tadp/Tnbk ratios stored in the lookup table inorder to determine which stored Tadp/Tnbk ratio the measured Tadp/Tnbkratio matches. The embedded controller 1282, in such an implementation,assumes that the power adapter 1202 coupled to the portable computer1206 has the power rating associated with the stored Tadp/Tnbk ratiothat matches the measured Tadp/Tnbk ratio. The embedded controller 1282is able to use the power rating of the power adapter 1202 to manage theoperation of the portable computer 1206 while coupled to that poweradapter 1202. In one exemplary implementation, if the power rating ofthe power adapter 1202 is greater than or equal to a full-power powerrating associated with the portable computer 1206, the embeddedcontroller 1282 operates the portable computer 1206 in a full-powermode. If the power rating of the power adapter 1202 is less than afull-power power rating associated with the portable computer 1206 butgreater than or equal to a minimum power rating associated with theportable computer 1206, the embedded controller 1282, in such anexemplary implementation, operates the portable computer 1206 in alow-power mode. If the power rating of the power adapter 1202 is lessthan a minimum power rating associated with the portable computer 1206,the embedded controller 1282, in such an exemplary implementation,powers off the portable computer 1206 (for example, by having theportable computer 1206 enter a “sleep” state in which battery chargingoccurs but the user is not otherwise able to use the portable computer1206).

The power adapter 1202 is shown in FIG. 12 as being directly coupled tothe portable computer 1206. The identification technique described inconnection 1200 can also be used to identify a power rating associatedwith any power adapter 1202 coupled to the portable computer 1206 via adocking station. The docking station provides a signal path between thecontrol terminal 564 of the power adapter 1202 and the control terminal1278 of the portable computer 1206 so that the identification circuit1280 is able to identify the power rating of the power adapter 1202coupled to the docking station as described above. The embeddedcontroller 1282 is able to determine when the power adapter 1202 iscoupled to the portable computer 1206 via a docking station and modifythe manner in which the embedded controller 1282 manages the operationof the portable computer 1206 while coupled to that power adapter 1202accordingly (for example, by taking into account the amount of powertypically consumed by the docking station when determining if the poweradapter 1202 is able to deliver sufficient power to operate the portablecomputer 1206 in fill-power mode and/or low-power mode).

The identification circuit 1280, in other embodiments, is implemented inother ways. One such alternative embodiment is illustrated in FIG. 13.

FIG. 13 is a block diagram of one embodiment of a computing system 1300.In the embodiment shown in FIG. 13, the power adapter 1202 of FIG. 12 iscoupled to a portable computer 1306 in order to provide power to theportable computer 1306 (and any external devices coupled to the portablecomputer 1306). Except as described here, the portable computer 1306 issimilar to the portable computer 1206 of FIG. 12 and similar componentsare referenced in FIG. 13 using the same reference numerals used in FIG.12 for those components. The identification circuit 1380 of the portablecomputer 1306 is similar to the identification circuit 1280 describedabove in connection with FIG. 12 except in the manner in which therespective gates of the first and second transistors 1232 and 1234 arecontrolled. A first gate-bias resistor 1354 and a first gate-controltransistor 1356 are coupled in series between a 5 Volt voltage level andground. The gate of the second transistor 1234 is coupled to a nodeformed between the first gate-bias resistor 1354 and the firstgate-control transistor 1356. The gate of the first gate-controltransistor 1356 is coupled to the output terminal GPO_2 of the embeddedcontroller 1282. A second gate-bias resistor 1350 and a secondgate-control transistor 1352 are coupled in series between a 5 Voltvoltage level and ground. The gate of the first transistor 1232 iscoupled to a node formed between the second gate-bias resistor 1350 andthe second gate-control transistor 1352. The gate of the secondgate-control transistor 1352 is coupled to the gate of the secondtransistor 1234.

When the embedded controller 1282 outputs a low value on GPO_2, thefirst gate-control transistor 1356 is turned off, which causes thevoltage developed at the gate of the second transistor 1234 to be a highvalue sufficient to turn on the second transistor 1234. When the secondtransistor 1234 is turned on, the second gate-control transistor 1352also turns on, which causes the voltage developed at the gate of thefirst transistor 1232 to be a low value sufficient to turn off the firsttransistor 1232. When the embedded controller 1282 outputs a high valueon GPO_2, the first gate-control transistor 1356 is turned on, whichcauses the voltage developed at the gate of the second transistor 1234to be a low value sufficient to turn off the second transistor 1234.When the second transistor 1234 is turned off, the second gate-controltransistor 1352 also turns off, which causes the voltage developed atthe gate of the first transistor 1232 to be a high value sufficient toturn on the first transistor 1232. In this way, the resistors 1354 and1350 and the first and second gate-control transistors 1356 and 1352 areused to replace the first and second inverting amplifiers 1239 and 1240of FIG. 12. The operation of the identification circuit 1380 and theembedded controller 1282 is otherwise the same as described above inconnection with FIG. 12.

FIG. 14 is a block diagram of one embodiment of a computing system 1400.In the embodiment shown in FIG. 14, a power adapter 1402 is directlycoupled to the portable computer 1406 (though in other embodiments, thepower adapter 1402 is coupled to the portable computer 1406 via one ormore intermediary devices such as a a docking station). Except asdescribed here, the power adapter 1402 and the portable computer 1406are similar to the power adapter 102 and portable computer 106 of FIG.1, respectively, and similar components are referenced in FIG. 14 usingthe same reference numerals used in FIG. 1 for those components. Thepower adapter 1402 comprises a pull-up resistor 1495 (also referred tohere as “resistor Radp” or just “Radp”) coupled across VOUT and thecontrol terminal 162 of the adapter interface 114 of the power adapter1402 in parallel with the control signal circuit 164. The pull-upresistor 1495 of the power adapter 1402, in the embodiment shown in FIG.14, has a resistance value that is much larger than the resistor 184used in the throttle signal circuit 180 of the 1406 to couple thecontrol signal 178 to ground. In one implementation of such anembodiment, the resistor 184 has a resistance value of 2 Kiloohms andthe pull-up resistor 1495 has a resistance value that is much largerthan 2 Kiloohms.

In the embodiment shown in FIG. 14, the portable computer 1406 comprisesboth the throttle signal circuit 180 and an identification circuit 1480similar to the identification circuit 1380 of FIG. 13 (and similarcomponents are referenced in FIG. 14 using the same reference numeralsused in FIG. 13 for such components). In such an embodiment, theinverting input of the comparator 186 of the throttle signal circuit 180is coupled to the control terminal 178 of the portable computer 1106using a Zener diode 1401 having a voltage drop of, for example, 6.8Volts. Also, in such an embodiment, the sawtooth wave used by thethrottle signal circuit 180 has a DC offset (for example, a sawtoothwave having a 1.0 Volt DC offset and a maximum amplitude of 2.0 Volts).When the power adapter 1402 is coupled to the portable computer 1406, atfirst, the control signal output by the control signal circuit 164 ofthe power adapter 1402 is zero. Because the pull-up resistor 1495 ismuch larger than the resistor 184, the current through the pull-upresistor 1495 will be insufficient to generate current on the controlterminal 178 sufficient to “turn on” the throttle signal circuit 180.The Zener diode 1401 used to couple the throttle signal circuit 180 tothe control terminal 178 of the portable computer 1406 does not affectthe identification circuit 1480 since the voltage developed at thecontrol terminal 178 is well less than the Zener voltage of the Zenerdiode 1401.

In such an embodiment, the output of the identification circuit 1480 ischecked by an embedded controller 1482 of the portable computer 1406when the power adapter 1402 is first coupled to the portable computer1406. The control signal circuit 164 of the power adapter 1402 typicallydoes not output the control signal during this time because the loadcurrent output by the power adapter 1402 typically does not rise abovethe throttle current threshold during this time or because the responsetime of the control signal circuit 164 is long enough that the controlsignal circuit 164 will not react (and output a control signal) duringthis time. After the embedded controller 1482 of the portable computer1406 measures Tadp and Tnbk, the embedded controller 1482 need notinteract with the identification circuit 1480 again while the same poweradapter 1402 is coupled to the portable computer 1406. Thereafter, theamount of power used by the portable computer 1406 is controlled usinginformation indicative of the amount of power output by the poweradapter 1402 (that is, using the control signal output by the controlsignal circuit 164) as described above in connection with FIG. 1.

In other embodiments, the techniques described above in connection withFIGS. 5-14 are used to identify other attributes of a power adaptercoupled to a portable computer. More generally, such techniques can beused by a portable computer to identify the power adapter that iscurrently coupled to the portable computer and the portable computer canuse such information to manage the operation of the portable computer(for example, by managing how the portable computer uses power).

1. A power adapter comprising: a power supply to supply power to atleast one electronic device; and a device interface to couple the poweradapter to the electronic device; wherein the device interface comprisesa terminal having an associated attribute for use by the electronicdevice to identify a power rating associated with the power adapter;wherein the power adapter outputs information indicative of an amount ofpower output by the power supply for use by the electronic device tocontrol the amount of power used by the electronic device by selectivetransitioning between a full power mode and a low power mode of theelectronic device.
 2. The power adapter of claim 1, further comprising aresistor coupled to the terminal.
 3. The power adapter of claim 1,wherein the attribute comprises a voltage level associated with a poweroutput of the power supply.
 4. The power adapter of claim 1, whereintransitioning to the low power mode comprises reducing a clock speed ofthe electronic device.
 5. A device comprising: an interface to receivepower from a power adapter; a terminal having a resistance coupled to itwhen the power adapter is coupled to the device, wherein the resistanceis indicative of an attribute associated with the power adapter, whereinthe device generates information indicative of the attribute associatedwith the power adapter based on at least the coupled resistance; and anidentification circuit that comprises: a first resistor coupled acrossthe terminal and a ground; a second and third resistors coupled inseries across an output voltage of the power adapter and the ground; anda comparator to output a signal indicative of the difference between afirst voltage developed at the terminal and a second voltage developedat a node formed between the second and third resistors; wherein theinformation indicative of the attribute associated with the poweradapter comprises the signal output by the comparator.
 6. A devicecomprising: an interface to receive power from a power adapter; aterminal having a resistance coupled to it when the power adapter iscoupled to the device, wherein the resistance is indicative of anattribute associated with the power adapter, wherein the devicegenerates information indicative of the attribute associated with thepower adapter based on at least the coupled resistance; and anidentification circuit that comprises: a first resistor coupled acrossthe terminal and a ground; a second, third, and fourth resistors coupledin series across an output voltage of the power adapter and the ground;a first comparator to output a first signal indicative of the differencebetween a first voltage developed at the terminal and a second voltagedeveloped at a first node formed between the second and third resistors;and a second comparator to output a second signal indicative of thedifference between the first voltage developed at the terminal and thirdvoltage developed at a second node formed between the third and fourthresistors; wherein the information indicative of the attributeassociated with the power adapter comprises the first signal output bythe first comparator and the second signal output by the secondcomparator.
 7. A device comprising: an interface to receive power from apower adapter; and a terminal having a resistance coupled to it when thepower adapter is coupled to the device, wherein the resistance isindicative of an attribute associated with the power adapter, whereinthe device generates information indicative of the attribute associatedwith the power adapter based on at least the coupled resistance;wherein: the power adapter comprises an adapter resistor, wherein theadapter resistor is coupled to the terminal when the power adapter iscoupled to the device; and the device further comprises anidentification circuit comprising a device resistor and a capacitor,wherein the identification circuit selectively couples the capacitor toone of the terminal and the device resistor.
 8. The device of claim 7,wherein the device: couples the capacitor to the adapter resistor anddetermines a first time associated with charging the capacitor via theadapter resistor; and couples the capacitor to the device resistor anddetermines a second time associated with charging the capacitor via thedevice resistor.
 9. The device of claim 8, wherein the information isgenerated based on the first and second times.
 10. The device of claim8, wherein the information is generated based on a ratio of the firstand second times.
 11. A device comprising: an interface to receive powerfrom a power adapter; and a terminal having a resistance coupled to itwhen the power adapter is coupled to the device, wherein the resistanceis indicative of an attribute associated with the power adapter, whereinthe device generates information indicative of the attribute associatedwith the power adapter based on at least the coupled resistance;wherein: the interface comprising a docking station interface to couplean electronic device to the device; the coupled resistance is coupled toa terminal of the docking station interface; and the docking stationdevelops a voltage associated with a power output level of the poweradapter at the terminal of the docking station interface.
 12. A systemcomprising: a computing device; a power adapter; a device interface tocouple the power adapter to the computing device; and wherein the deviceinterface comprises a terminal having a resistance indicative of anattribute associated with the power adapter when the power adapter iscoupled to the device interface, for use by the computing device toidentify the attribute associated with the power adapter; wherein thepower adapter outputs information indicative of an amount of poweroutput by the power adapter for use by the computing device to controlthe amount of power used by the computing device by selectivetransitioning between a full power mode and a low power mode of thecomputing device.
 13. The system of claim 12, further comprising aresistor coupled to the terminal.
 14. The system of claim 12, whereinthe attribute comprises a power level associated with the power adapter.15. The system of claim 12, wherein transitioning to the low power modecomprises reducing a clock speed of the computing device.
 16. The systemof claim 12, wherein the information indicative of the amount of poweroutput by the power adapter is a voltage level associated with the poweroutput of the power adapter.
 17. The system of claim 16, wherein thevoltage level is output on the terminal.
 18. The system of claim 12,wherein the power adapter outputs the information once a predeterminedpower level is exceeded.